It is proposed to study specifically the cellular regulation of template and metabolic pathways involved in the synthesis of dimethylnitrosamine (DMN)-demethylase, a microsomal oxidase which dealkylates DMN, yielding diazomethane or carbonium ion the proximate carcinogen of DMN. These studies will include experiments designed to provide: (1) information on the hormonal regulation of mixed-function oxidase levels; (2) knowledge on the turnover of this enzyme in the presence and absence of "inducer" compounds, and on the possibility of a common site of action for "inducer" hydrocarbons and phenobarbital; and (3) the background for extending the generality of these findings on the inhibition of DMN dealkylation and hepatocarcinogenesis to other nitrosamines.